1. Field of the Invention
The invention relates to an automatic circuit for blocking the transmission of identifying information of a calling party on a telephone network.
2. Description of Prior Art
Telephone companies presently provide Caller ID service whereby to identify, to a party receiving a telephone call, the telephone number of the calling party. With this service, the telephone number of the calling party is transmitted, along with the ringing signal and, if the receiving party has a special receiving device for this purpose, the number of the calling party will be displayed on this special device.
There are times when it is inconvenient to a calling party to have his phone number disclosed to the receiving party. For example, the calling party may be calling from an unlisted telephone number which he does not wish to disclose to the receiving party. For this reason, the telephone companies providing the above services have received complaints and they therefore now provide a further service whereby, on action of the calling party, the transmission of the identifying information will be blocked.
This action, which can be taken by any telephone subscriber, consists of first registering with the telephone company. Thereafter, before dialing any telephone number, the caller would dial a predetermined code, for example, *67.
The predetermined code is transmitted to a computer of the telephone company which then blocks the transmission of the identifying information.
One of the problems with this solution is that it is inconvenient to continually dial the predetermined code before dialing any telephone number. In addition, it is possible that a calling party will forget to dial the predetermined code whereupon his telephone number will be transmitted.